摘要:

Percentage pollen diagrams are presented and analysed by step‐wise discriminant analysis. Arboreal taxa show little variation between communities. Non‐arboreal, local taxa display substantial variability, but are good indicators of community composition and structure, and provide reliable elements for the palynological characterization of communities. The discriminant analysis indicates a distinctiveness for most communities that is surprisingly high considering the small size of many of the vegetation units within the mos

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01030.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Wood samples from above the present‐day pine limit were collected from within a limited area in central Sweden. New dates from an intensively investigated part of that area all fall within the period 8550 ± 110 to 4270 ± 9014C years B. P. No evidence at present exists to suggest that any drastic change, or fluctuations, in the pine tree‐limit, took place within that period. Some dates support the view that the present‐day altitude of the pine tree‐limit was established during the historic period and perhaps is still

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01031.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Short cores of soft sediment, used in studying the pollution history of lakes, can be obtained with a plastic tube fitted with a piston and piston wire. If the sediments of deep water are annually laminated (and thus difficult to sample without disturbance) or contain excess gas (which can disrupt the stratigraphy during its escape), a short ‘core’ can be acquired by producing a frozen crust on a tube filled with dry ice and butanol.A continuous core of soft lake sediment at least 7 m long can be obtained in a single drive beneath deep water with a hand‐driven piston corer. Such a core assures the complete continuity necessary for counting annual laminations or for making close‐interval analyses without fear of gaps, and it provides the uniform orientation required for measurements of paleomagnetic dir

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01032.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Synoptically mapped faunal abundance and faunal composition data, derived from a suite of 24 Norwegian Sea cores, were used to derive sea‐surface temperatures for the last glacial maximum (18,000 B.P.), the last interglacial (120,000 B.P.), and isotope stage 5a (82,000 B.P.). Surface circulation and ice cover reconstructions for these three times, deduced from the sea‐surface temperatures, suggest the following conclusions: (1) During glacial periods, Norwegian Sea surface circulation formed a single, sluggish, counterclockwise gyre that was caused by wind drag on the ubiquitous sea ice cover; (2) the last interglacial was characterized by a circulation pattern similar to that of today except that the two counterclockwise gyres were displaced toward the east and were more vigorous than they are today. This circulation pattern forced the Norwegian Current into a position close to the coast of Norway and permitted formation of a strong east‐west temperature gradient close to the Scandinavian landmass; (3) interglacial periods prior to 120,000 B.P. had similar climatic conditions to the 82,000 B.P. level and were characterized by a weak two‐gyre circulation pattern. The southern gyre, driven by wind stress in summer months, was ice covered in winters. The northern gyre had little open water even in summers and was primarily formed by wind drag on sea ice. Atmospheric modifications resulting from these circulation patterns and sea ice conditions produced varying climatic conditions in Scandinavia during interglacials prior to the Holocene. The climate was probably warmer and moister during the last interglacial (Eemian) than it is today. Other interglacials during the last 450,000 years, but prior to the Eemian, were probably colder and drier as the Norwegian Sea was not an important source of heat and m

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01033.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

A bed of peat resting on sands and gravels and reaching the present‐day ground surface, was investigated for beetles, and seven radiocarbon dates were obtained. The beetles indicated that the lowest layers of the peat, dated around 12,000 B.P., were laid down in boggy conditions in a treeless landscape under a climatic regime which was rather cooler than present day. Two quite sudden changes in the aspect of the fauna then followed. The first was the incoming of an assemblage indicative of a climate of arctic severity. This layer was not dated but if the rate of deposition was constant during this period it must have been around 11,000 B. P. The second change was the equally rapid disappearance of this northern fauna about 1000 years later. Succeeding layers then contained beetles suggesting conditions as warm as those of the present day, with species indicating both coniferous and deciduous trees appearing before 9500 B.

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01034.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01035.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01036.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1980.tb01037.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY